Extreme ultraviolet light source, exposure apparatus, and integrated rotary structure fabricating method

ABSTRACT

In some embodiments of the disclosed subject matter, an extreme ultraviolet (EUV) light source is provided. The EUV light source comprises: a droplet nozzle array droplet nozzle array comprising multiple nozzles arranged in a ring, the nozzles are configured for sequentially ejecting droplets towards an annular radiation position; a laser source for generating a laser beam, wherein the laser beam is controlled to rotate and sequentially bombard the droplets that reach the annular radiation position; and an integrated rotary structure located between the droplet nozzle array and the laser source, the integrated rotary structure includes: a condenser mirror comprising a first surface and a second surface opposing to the first surface, and a motor driving shaft that is integrally connected with the condenser mirror.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the priority of Chinese patent application No.201510363583.9, filed on Jun. 26, 2015, the entire content of which isincorporated herein by reference.

TECHNICAL FIELD

The disclosed subject matter generally relates to semiconductortechnology and, more particularly, relates to an extreme ultraviolet(EUV) light source, an exposure apparatus, and a method for fabricatingan integrated rotary structure.

BACKGROUND

Photolithography, an important step in a manufacturing process for asemiconductor device, can be used to form a resist pattern in a resistlayer by using an exposure process and a development process. Along withthe continuous improvement of chip integration, a feature size ofphotolithography continues to decrease.

A minimum feature size of photolithography is determined by theresolution (R) of an exposure apparatus. The resolution (R) of anexposure system satisfies the following formula: R=kλ/(NA), where k is acoefficient relating to the exposure process, λ represents a wavelengthof the exposure light source, NA is the numerical aperture of theoptical system of the exposure apparatus. According to the formula, theresolution of the exposure apparatus can be increased by increasing thenumerical aperture of the optical system or by reducing the wavelengthof the exposure light source.

For increasing the numerical aperture of the optical system to improvethe resolution, due to a rigor demanding of the minimum feature size ofthe next-generation photolithography technology, a very large opticalnumerical aperture is required. However, the increasing of the numericalaperture not only complicates the preparation and modulation of thephotolithography system, but also restricts the depth of focus of theoptical system.

For reducing the wavelength of the exposure light source for improvingthe resolution, the extreme ultraviolet (EUV) light source is the latestdeveloped light source. An EUV light source can generate an exposurelight with a 13.5 nm wavelength. So the usage of an EUV light source inan exposure system can obtain a small feature size of photolithography.

An existing method to produce extreme ultraviolet (EUV) light includesuse of laser produced plasma (LPP) radiation mode. A laser beamgenerated by a laser source may bombard a tin (Sn) target for excitingplasma. The excited plasma can radiate extreme ultraviolet (EUV) light.

A structure of an existing EUV light source can be referred to FIG. 1.The EUV light source includes a tin droplet nozzle 101, a laser source103, lens unit 105, and a condenser lens 107. The tin droplet nozzle 101can downwardly eject tin droplets 102. The laser light source 103 cangenerate a laser beam 104. The laser beam 104 can be convergent aftergoing through lens unit 105. The convergent laser beam can bombard tindroplets 102 to generate plasma. The plasma can radiate extremeultraviolet light 108. The condenser 107 can collect extreme ultravioletlight 108 and gather the extreme ultraviolet light 108 at the centralfocus 109.

However, the power of the existing EUV light source is still too low tomeet the production requirements.

Accordingly, it desirable to provide an extreme ultraviolet (EUV) lightsource, an exposure apparatus, and a method for fabricating anintegrated rotary structure to at least partially alleviate one or moreproblems set forth above and to solve other problems in the art.

BRIEF SUMMARY

In accordance with some embodiments of the disclosed subject matter, anextreme ultraviolet lithography (EUV) light source, an exposureapparatus, and a method for fabricating an integrated rotary structureare provided.

One aspect of the disclosed subject matter provides an extremeultraviolet light source, comprising: a droplet nozzle array dropletnozzle array comprising a plurality of nozzles arranged in a ring,wherein the plurality of nozzles are configured for sequentiallyejecting droplets towards an annular radiation position; a laser sourcefor generating a laser beam, wherein the laser beam is controlled torotate and sequentially bombard the droplets that reach the annularradiation position, wherein the bombarded droplets form a plasma thatradiates an extreme ultraviolet light; and an integrated rotarystructure located between the droplet nozzle array and the laser source,wherein the integrated rotary structure includes: a condenser mirrorcomprising a first surface and a second surface opposing to the firstsurface, and a motor driving shaft that is integrally connected with thecondenser mirror, wherein the first surface faces the droplet nozzlearray, the second surface is connected with the motor driving shaft, thefirst surface comprises an eccentric and inclined elliptical reflectivesurface and a non-reflective surface surrounding the ellipticalreflective surface, and the elliptical reflective surface is configuredfor collecting and reflecting the extreme ultraviolet light, andconverging the extreme ultraviolet light at a central focus under theannular radiation position.

In some embodiments, the integrated rotary structure further comprises athrust bearing integrally connected with the motor driving shaft.

In some embodiments, the plurality of nozzles are equidistantly arrangedin the ring; and each nozzle is inclined at a first angle toward acenter of the ring.

In some embodiments, the annular radiation position has a ring shape;the annular radiation position is parallel to the ring of the pluralityof nozzles; and a radius of the annular radiation position is smallerthan a radius of the ring of the plurality of nozzles.

In some embodiments, a connection between a center of the annularradiation position and a center of the ring of the plurality of nozzlesis perpendicular with the annular radiation position.

In some embodiments, the central focus is located on an extension lineof the connection between a center of the annular radiation position anda center of the ring of the plurality of nozzles.

In some embodiments, the connection between the center of the annularradiation position and the center of the ring of the plurality ofnozzles coincides with a first optical axis of the elliptical reflectivesurface.

In some embodiments, the extreme ultraviolet light source furthercomprises a brushless motor configured for driving the integrated rotarystructure to rotate with respect of the first optical axis.

In some embodiments, the elliptical reflective surface has a secondoptical axis going through the central focus; and an inclined angle ofthe elliptical reflective surface is equal to an angle between the firstoptical axis and the second optical axis.

In some embodiments, the extreme ultraviolet light source furthercomprises: a first through hole in the center of the ellipticalreflective surface; a second through hole in the motor driving shaft;and a third through hole in the thrust bearing; wherein the firstthrough hole, the second through hole, and the third through hole areinterconnected with each other to form a laser beam incident channel;and wherein the laser source comprises: a laser device configured forgenerating the laser beam; a focusing lens located in the first throughhole and fixed with the condenser mirror, wherein the focusing lens isconfigured for focusing the laser beam to the annular radiationposition.

In some embodiments, the laser source further comprises a reflectingdevice for reflecting the laser beam generated by the laser device intothe laser beam incident channel.

In some embodiments, the extreme ultraviolet light source furthercomprises: a control unit configured for synchronously outputting afirst signal and a second signal, wherein: the first signal controls theplurality of nozzles to sequentially eject droplets, and the secondsignal controls the brushless motor to drive the integrated rotarystructure to make the elliptical reflective surface and the focusinglens rotate synchronously.

In some embodiments, the laser device is a pulses pump laser device.

In some embodiments, the first signal controls the plurality of nozzlesto sequentially eject droplets in a certain direction, wherein eachnozzle ejects a droplet after a first lag period of an instance that anadjacent nozzle ejects a droplet.

In some embodiments, the first lag period equals a time interval betweentwo adjacent laser pulses generated from the pulses pump laser device.

In some embodiments, the first signal controls each nozzle tocontinuously eject droplets; a time interval between two adjacentejecting is a second lag period; and the second lag period equals to anumber of the plurality of nozzles times the first lag period.

Another aspect of the disclosed subject matter provides an exposureapparatus, comprising: an extreme ultraviolet light source, comprising:a droplet nozzle array comprising a plurality of nozzles arranged in aring, wherein the plurality of nozzles are configured for sequentiallyejecting droplets towards an annular radiation position; a laser sourcefor generating a laser beam, wherein the laser beam is controlled torotate and sequentially bombard the droplets that reach the annularradiation position, wherein the bombarded droplets form a plasma thatradiates an extreme ultraviolet light; and an integrated rotarystructure located between the droplet nozzle array and the laser source,wherein the integrated rotary structure comprises: a condenser mirrorcomprising a first surface and a second surface opposing to the firstsurface, and a motor driving shaft that is integrally connected with thecondenser mirror, wherein the first surface faces the droplet nozzlearray, the second surface is connected with the motor driving shaft, thefirst surface comprises an eccentric and inclined elliptical reflectivesurface and a non-reflective surface surrounding the ellipticalreflective surface, and the elliptical reflective surface is configuredfor collecting and reflecting the extreme ultraviolet light, andconverging the extreme ultraviolet light at a central focus under theannular radiation position.

Another aspect of the disclosed subject matter provides a method forfabricating an integrated rotary structure, comprising: providing acylinder material, comprising a circular side wall, a third surface atone end of the circular side wall and a fourth surface at another end ofthe circular side wall opposing to the third surface; machining thethird surface of the cylinder material to form an elliptical reflectivesurface, wherein: a second optical axis of the elliptical reflectivesurface coincides with an axis of the cylinder material passing throughcenters of the third and fourth surfaces, and the ellipsoidal reflectivesurface sinks into the cylinder material and by a first depth; forming afirst through hole going through a center of the elliptical reflectivesurface; machining the circular side wall of the cylinder material toform a fifth surface and a sixth surface, wherein: both the fifthsurface and the sixth surface have a first angle with the second opticalaxis, and a central symmetrical axis of the fifth surface and the sixthsurface coincides with a first optical axis of the elliptical reflectivesurface; and using the fifth surface and the sixth surface as holdingplanes, machining the third surface to form a curved non-reflectivesurface surrounding the elliptical reflective surface.

In some embodiments, forming the curved non-reflective surfacecomprises: forming a first cambered surface that is in contact with orclose to a high point of the elliptical spherical reflective surface;and forming a second cambered surface that is in contact with or closeto a low point of the elliptical spherical reflective surface.

In some embodiments, the method further comprises: removing a portion ofthe cylinder material along the fifth surface and the sixth surface toform a curved second surface, wherein the second surface opposites afirst surface comprising the non-reflective surface and the ellipticalreflective surface; machining a remaining portion of the cylindermaterial along the fifth surface and the sixth surface to form a motordriving shaft connecting with the second surface; and machining aremaining portion of the cylinder material along the fourth surface, thefifth surface, and the sixth surface to form a thrust bearing connectingwith the motor driving shaft.

Other aspects of the disclosed subject matter can be understood by thoseskilled in the art in light of the description, the claims, and thedrawings of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings are merely examples for illustrative purposesaccording to various disclosed embodiments and are not intended to limitthe scope of the present disclosure.

FIG. 1 is a schematic structural diagram of an existing EUV lightsource;

FIGS. 2-9 are schematic structural diagrams of exemplary EUV lightsources in accordance with some embodiments of the disclosed subjectmatter;

FIG. 10 is a control signal diagram of an exemplary EUV light source inaccordance with some embodiments of the disclosed subject matter; and

FIGS. 11-17 illustrate schematic structures of an exemplary integratedrotary structure corresponding to certain stages of a fabricatingprocess consistent with some embodiments of the disclosed subjectmatter.

DETAILED DESCRIPTION

Various objects, features, and advantages of the disclosed subjectmatter can be more fully appreciated with reference to the followingdetailed description of the disclosed subject matter when considered inconnection with the following drawings, in which like reference numeralsidentify like elements. It should be noted that the following drawingsare merely examples for illustrative purposes according to variousdisclosed embodiments and are not intended to limit the scope of onedisclosure. In an actual production, a disclosed subject matter mayinclude three spatial dimensions of length, width and depth.

It is apparent that the described embodiments are some but not all ofthe embodiments of the present invention. Based on the disclosedembodiments, persons of ordinary skill in the art may derive otherembodiments consistent with the present disclosure, all of which arewithin the scope of the present invention.

The power of existing extreme ultraviolet (EUV) light sources forgenerating EUV is around 10 W to 30 W. But in an actual photolithographyprocess, a required power of a light source can reach 250 W. So, theexisting EUV light sources cannot generate EUV light that meets theactual production requirements.

In existing EUV light sources, a tin droplet nozzle mechanicallycontrols the ejection of tin droplets to make neighboring tin dropletsbe spatially separated. A laser beam can bombard each tin droplet toform tin plasma. The tin plasma can produce extreme ultraviolet (EUV)radiation. If two neighboring tin droplets has a too small distance, ortwo tin droplets stick together, when the laser beam bombard a currenttin droplet, the generated tin plasma debris can affect the followingtin droplet, resulting in many problems, such as poor laser beambombardment, difficulty in collecting extreme ultraviolet radiation, andother issues. All these problems can reduce the power of the EUV lightsource.

In order to ensure integrity of each tin droplet and a certain distancebetween adjacent tin droplets, an ejecting frequency limit of theexisting mechanically controlled tin droplet nozzle is about 100 KHz.Since the number of ejecting tin droplets per unit time of the existingtin droplets nozzle is limited, the number of tin droplets per unit timethat are bombarded by the laser beam is limited. Thus an amount ofplasma generated by bombarding the tin droplets and an amount of extremeultraviolet light radiated from the plasma are also limited. Thus anamount of extreme ultraviolet light convergence on the central focus perunit time is limited. Therefore, the power of the existing EUV lightsource is small.

Accordingly, the disclosed subject matter provides an extremeultraviolet lithography (EUV) light source, an exposure apparatus, and amethod for fabricating an integrated rotary structure, which aredirected to solve the problem set forth above or other problems in theart.

In accordance with some embodiments, an extreme ultraviolet light sourcecan be provided.

The extreme ultraviolet light source can include a droplet nozzle arraycomprising a plurality of nozzles arranged in a ring. The plurality ofnozzles are configured for sequentially ejecting droplets downwardly toan annular radiation position.

The extreme ultraviolet light source can further include a laser sourcefor generating a laser beam. The laser beam is controlled to rotate andsequentially bombard the droplets that reach the annular radiationposition.

The extreme ultraviolet light source can further include an integratedrotary structure located in between of the droplet nozzle array and thelaser source. The integrated rotary structure can include a condensermirror comprising a first surface and a second surface opposing to thefirst surface, and a motor driving shaft that is integrally connectedwith the condenser mirror. The first surface faces the droplet nozzlearray. The second surface is connected with the motor driving shaft. Thefirst surface comprises an eccentric and inclined elliptical reflectivesurface and a non-reflective surface surrounding the ellipticalreflective surface. The elliptical reflective surface is configured forcollecting and reflecting extreme ultraviolet light radiated frombombarded droplets, and converging the extreme ultraviolet light at acentral focus under the annular radiation position.

The disclosed extreme ultraviolet light source can increase the supplyof droplets per unit time, and maintain a certain distance betweenadjacent droplets. The laser beam can rotate and sequentially bombardthe droplets to form extreme ultraviolet light. Since no droplet thatreaches the annular radiation position is wasted, the amount ofgenerated extreme ultraviolet light may be increased. Also, theelliptical reflective surface of the rotating condenser mirror cancollect and reflect the extreme ultraviolet light, and converge theextreme ultraviolet light at the central focus. Therefore, a power ofthe extreme ultraviolet light at the central focus can be increased.

Referring to FIGS. 2-9, schematic structural diagrams of exemplary EUVlight sources are shown in accordance with some embodiments of thedisclosed subject matter.

A structure of an EUV light source is illustrated in FIG. 2, and astructure of a condenser lens of the EUV light source is illustrated inFIG. 3.

The EUV light source can include droplet nozzle array 201, laser source203, and integrated rotary structure 215.

In some embodiments, the droplet nozzle array 201 includes multiplenozzles 21 that are arranged along a circular ring. The multiple nozzles21 can successively eject droplets downwardly towards the annularradiation position 202.

In some embodiments, the laser source 203 can generate a laser beam 31that is incident from above into the droplet nozzle array 201. The laserbeam 31 can rotate and scan, and successively bombard the droplets thatreach the annular radiation position 202. A plasma radiating EUV lightcan be formed by bombarding the droplets.

The integrated rotary structure 215 is located between the dropletnozzle array 201 and the laser source 203. In some embodiments, theintegrated rotary structure 215 includes a condenser mirror 214, and amotor driving shaft 217 that is integrally connected with the condensermirror 214.

The condenser mirror 214 includes a first concave surface 233 and asecond concave surface 234 opposing to the first concave surface 233.The first concave surface 233 faces to the droplet nozzle array 201. Thesecond surface 234 is connected with the motor driving shaft 217. Insome embodiments, the first concave surface 233 includes an ellipticalreflective surface 231 that is eccentric and inclined, and anon-reflective surface 232 surrounding the elliptical reflective surface231.

When the integrated rotary structure 215 is rotating, the ellipticalreflective surface 231 can converge the radiating extreme ultravioletlight on a central focus 220 under the annular radiation position 202.

In some embodiments, the EUV light source further includes a dropletsupply chamber (not shown in the figure) for storing the dropletmaterial for forming the droplets. The droplet supply chamber can beconnected with the multiple nozzles 21 through intermediate pipes (notshown in the figures). The droplet material stored in the droplet supplychamber can form multiple droplets and be ejected by the multiplenozzles 21.

In some embodiments, the droplet nozzle array 201 further includesmultiple switches corresponding to the multiple nozzles 21 separately.Each switch can control a correspond nozzle 21 for ejecting droplets. Insome embodiments, the switches may be placed on the intermediate pipesbetween the nozzles 21 and the droplet supply chamber. The flows of thedroplet material in the intermediate pipes can be controlled by theswitches, so that each nozzle 21 can intermittently eject droplets 22towards the annular radiation position 202. The multiple switches can bemechanical switches controlled by electrical signals to open and closethe intermediate pipes to realize intermittently ejecting droplets 22.

In some embodiments, the multiple nozzles 21 are arranged in an annularregion. The spaces between adjacent nozzles in the annular region areequal. Each nozzle 21 is inclined at a first angle A toward the centerof the annular region. In some embodiments, the first angle A has arange between 20 and 40 degrees. Each nozzle 21 has a same caliber. Thelower edges of the multiple nozzles 21 are in a plane that is parallelto the plane of the annular radiation position 202. Thus every dropletejected from the multiple nozzles 21 can travel a same distance to theannular radiation position 202. In some embodiments, the plane of thelower edges of the multiple nozzles 21 is parallel to the X-Y axisplane.

In some embodiments, the droplet material can be tin, tin alloy, tincompound, lithium, or xenon. The tin compound may be SnBr₄, SnBr₂, SnH₄,etc. The tin alloy may be gallium-tin alloy, gallium, indium-tin alloy,tin-indium-gallium alloy, etc.

Depending on the different selected droplet material, the temperature ofthe droplets 22 on the annular radiation position 202 can also bedifferent.

The annular radiation position 202 is an annular region located belowthe droplet nozzle array 201. The plane of the annular radiationposition 202 is parallel to the plane of the lower edges of the multiplenozzles 21. In some embodiments, the plane of the annular radiationposition 202 is parallel to the X-Y axis plane. In some embodiments, aradius of the annular region of the annular radiation position 202 isless than a radius of the annular region of the multiple nozzles 21. Thecenter of the annular region of the annular radiation position 202 isbelow the center of the annular region of the multiple nozzles 21.

In some embodiments, the EUV light source further includes a firstoptical axis 205. The first optical axis 205 goes through the center ofthe annular region of the annular radiation position 202, the center ofthe annular region of the multiple nozzles 21, and the axis of theintegrated rotary structure 215. The central focus 220 is located belowthe annular radiation position 202, and on the connection extension lineof the center of the annular region of the annular radiation position202 and the center of the annular region of the multiple nozzles 21.

Referring to FIG. 3, an enlarged schematic structural diagram of anexemplary condenser lens is shown in accordance with some embodiments ofthe disclosed subject matter.

The condenser mirror 214 can have a bowl-shape. The condenser mirror 214includes a first concave surface 233 and a second concave surface 234opposing to the first concave surface 233. The first concave surface 233faces to the droplet nozzle array 201. The second surface 234 isconnected with the motor driving shaft 217. In some embodiments, thefirst concave surface 233 includes an elliptical reflective surface 231that is eccentric and inclined, and a non-reflective surface 232surrounding the elliptical reflective surface 231.

The elliptical reflective surface 231 can collect the radiating extremeultraviolet light formed by bombarding the droplets 22 on the annularradiation position 202, and converge the radiating extreme ultravioletlight on the central focus 220 under the annular radiation position 202.The collection and convergence of the extreme ultraviolet light followsthe law of reflection. The non-reflective surface 232 does not reflectthe extreme ultraviolet light, or even some extreme ultraviolet portionreflected by the non-reflective surface 232 does not converge on thecentral focus 220.

The first optical axis 205 goes through the center of the condensermirror 214, and coincides with the axis of the condenser mirror 214. Theelliptical reflective surface 231 has a second optical axis 206 thatgoes through the center of the elliptical reflecting surface 231 andcoincides with the axis of the elliptical reflecting surface 231.

The elliptical reflecting surface 231 is eccentric and inclined. Thecenter of the elliptical reflecting surface 231 has a distance from thecenter of the condenser mirror 214. An inclination angle of theelliptical reflecting surface 231 equals to an angle between the firstoptical axis 205 and the second optical axis.

Since the elliptical reflecting surface 231 is eccentric and inclined,when the condenser mirror 214 is rotating, the elliptical reflectingsurface 231 can successively collect the extreme ultraviolet lightradiated by the bombarded droplets that are sequentially reach theannular radiation position 202, and can converge the extreme ultravioletlight on the central focus 220.

In some embodiments, the annular radiation position 202 corresponds to afirst focus of the elliptical reflective surface 231, while the centralfocus 220 corresponds to a second focus of the elliptical reflectivesurface 231. When the condenser mirror 214 is rotating, the first focusof the elliptical reflective surface 231 is moving along with theannular radiation position 202, while the second focus of the ellipticalreflective surface 231 is fixed at the position of the central focus220. Therefore, when the condenser mirror 214 is rotating, the generatedextreme ultraviolet light at the first focus (or annular radiationposition 202) can be collected and reflected by the ellipticalreflective surface 231. The reflected extreme ultraviolet light canconverge on the second focus (or the central focus 220).

In some embodiments, besides the elliptical reflective surface 231, thecondenser mirror 214 further includes a non-reflective surface 232surrounding the elliptical reflective surface 231. The non-reflectivesurface 232 can balance the mass of the condenser mirror 214 to make amass distribution of the condenser mirror 214 being centrosymmetric tothe first optical axis 205. Thus when the condenser mirror 214 ishigh-speedily rotating around the first optical axis 205, the integratedrotary structure can maintain a good dynamic balance to prevent anoffset or twisted from the condenser mirror 214.

In some embodiments, the condenser mirror 214 can further include afirst through hole 237. The first through hole 237 can penetrate a firstsurface 233 and a second surface 234 of the condenser mirror 214. Thefirst surface 233 includes the elliptical reflective surface 231 and thenon-reflective surface 232.

Referring to FIGS. 4 and 5, schematic structural diagrams of theintegrated rotary structure are shown in accordance with someembodiments of the disclosed subject matter.

The center of the first through hole 237 coincides with the center ofthe elliptical reflective surface 231. The first through hole 237 isused as channel for the incident laser beam, and is also used to placethe focusing lens 236. The focusing lens 236 is used for converging theincident laser beam 31 to focus on the annular radiation position 202,which can be in accordance with FIG. 2 described above.

The focusing lens 236 is located in the first through hole 237. Thefocusing lens 236 can be fixedly connected to the side wall of the firstthrough hole 237. The axis of the focusing lens 236 is parallel to thefirst optical axis 205. An extension line of the axis of the focusinglens 236 goes through the annular radiation position 202, which can bein accordance with FIG. 2 described above.

In some embodiments, the integrated rotary structure 215 furtherincludes a motor driving shaft 217. A center axis of the motor drivingshaft 217 coincides with the first optical axis 205. The motor drivingshaft 217 is integrally connected with the second surface 234 of thecondenser mirror 214. For example, the motor driving shaft 217 and thecondenser mirror 214 can be integrally fabricated by a single subject.The motor driving shaft 217 and the condenser mirror 214 can be made bya same material. Thereby a mechanical strength of the integral rotarystructure 215 can be increased.

The motor driving shaft 217 is a rotor shaft of a brushless motor. Thebrushless motor can further include stator coils (not shown in thefigures) surrounding the motor driving shaft 217, and a mounting bracketof stator coil (not shown in the figures) disposed outward of the statorcoils. Driven by the brushless motor, the motor driving shaft 217 canrotate around the first axis 205. Since the motor driving shaft 217 isintegrally connected to the condenser mirror 214, when the motor drivingshaft 217 is rotating, the corresponding condenser mirror 214 and thefocusing lens 236 are also rotating around the first optical axis 205.During the rotating process, a laser beam focused by the focusing lens236 can sequentially bombard the droplets 22 that reach the annularradiation position 202. The radiated extreme ultraviolet light can becollected and reflected by the elliptical reflective surface 231 of thecondenser mirror 214, and be convergent on the central focus 220.

The motor driving shaft 217 has a second through hole connecting to thefirst through hole 237 in the condenser mirror 214. An inner diameter ofthe second through hole is larger than an inner diameter of the firstthrough hole 237. An axis of the second through hole coincides with thefirst optical axis 205.

The integrated rotary structure 215 also includes a thrust bearing 230that is integrally connected with the motor driving shaft 217. The axisof the thrust bearing 230 coincides with the first optical axis 205. Athird through hole is in the thrust bearing 230. The third through isconnected to the second through hole in the motor driving shaft 217. Aninner diameter of the third through hole is equal to the inner diameterof the second through hole. An axis of the third through hole coincideswith the first optical axis 205. Both the second through hole and thethird through hole are configured as a laser beam incident channel.

The thrust bearing 230 is connected to a mounting bracket (not shown inthe figures) to make the integrated rotary structure 215 hanging in theair, and enabling to rotate when driven by the brushless motor.

Referring to FIG. 4, FIG. 6 and FIG. 7, the thrust bearing 230 includesinner rings 235 and 238, outer rings 240 and 241, and multiple rollingelements 239 located between the inner rings 237, 238 and outer rings240, 241.

The inner rings 235 and 238 are connected integrally with the motordriving shaft 217. The third through hold is inside of the inner rings235 and 238. The inner rings include a first inner ring 235 and a secondinner ring 238 that is integrally connected with the first inner ring235. The first inner ring 235 and the second inner ring 238 areprotruded from the outer surface of the motor driving shaft 217. Theouter surfaces of the first inner ring 235 and the second inner ring 238are inclined to the first axis 205. An angle between the outer surfaceof the first inner ring 235 and the outer surface of the second innerring 238 is less than 90 degrees. In one embodiment, a cross-sectionalview of the outer surface of the first inner ring 235 and the outersurface of the second inner ring 238 is “<>” shape.

The multiple rolling elements 239 may be cylindrical or spherical balls.The multiple rolling elements 239 can include multiple first rollingelements locating on the outer surface of the first inner ring 235, andmultiple second rolling elements locating on the outer surface of thesecond inner ring 238.

The outer rings configuring for confining the multiple rolling elements239 are connected to the mounting bracket. The outer rings include afirst outer ring 241 for confining the multiple first rolling elements,and a second outer ring 240 for confining the multiple second rollingelements. Thus the multiple first rolling elements can roll between theouter surface of first inner ring 235 and the inner surface of firstouter ring 241, and the multiple second rolling elements can rollbetween the outer surface of second inner ring 238 and the inner surfaceof second outer ring 240.

In some embodiments, the inner rings of the thrust bearing 230 and themotor driving shaft 217 are integrally connected with each other toenhance the mechanical strength of integral rotary structure 215. Theinner rings of the thrust bearing 230 include two inclined outersurfaces intersecting with each other. Multiple first rolling elementsand second rolling elements are respectively provided to contact to thetwo inclined outer surfaces. And two outer rings are provided forconfining the first rolling elements and second rolling elements. Thus,the thrust bearing 230 has very mall swings in both vertical andhorizontal directions due to being evenly forced. Additionally, thecondenser mirror 214 has very mall swings in both vertical andhorizontal directions during rotating. Therefore, an intensityuniformity of the extreme ultraviolet light at the central focus 220 canbe improved.

In some other embodiments, the thrust bearing 230 and the motor drivingshaft 217 may be separate parts, and can be fixedly connected with eachother by welding or other suitable method. For example, the inner ringsof the thrust bearing 230 can be welded to the outer surface of one endof the motor driving shaft 217.

Referring to FIGS. 8 and 9, enlarged schematic structural diagrams ofthe droplet nozzle array 201 are shown in accordance with someembodiments of the disclosed subject matter. FIG. 8 is a perspectiveview of the droplet nozzle array 201 and FIG. 9 is a top view of thedroplet nozzle array 201.

As illustrated, the droplet nozzle array 201 includes multiple nozzles21 that are annularly arranged. The multiple nozzles 21 successivelyinclude first nozzle 21 a 1, second nozzle 21 a 2, third nozzle 21 a 3,and the Nth (N>3) nozzle 21 an.

In the droplet nozzle array 201, a distance between two adjacent nozzles21 can be a fixed value. The multiple nozzles 21 can regularly ejectdroplets 22 in an annular sequence to the annular radiation position202. A distance between two adjacent droplets in the annular sequence isalso a fixed value. Thus droplet nozzle array 201 can sequentially ejectdroplets to the annular radiation position 202. A rotational scanninglaser beam can successively bombard the droplets one by one that reachesthe annular radiation position 202. A droplet to be bombarded does notbe effected by the plasma debris formed by bombarding the antecedentdroplet. It should be noted that, the distance between two adjacentnozzles 21 is an arc length of the annular ring of the lower edges ofthe nozzles 21.

In one particular embodiment, a distance between two adjacent dropletsat the annular radiation position 202 is around 45 microns to 75microns. A size of droplets 22 ejected from the nozzles 21 is around 25microns to 35 microns.

The multiple nozzles 21 can eject multiple droplets 22 downwardly to theannular radiation position 202 by the following process. The firstnozzle 21 a 1 ejects a first droplet at a first instance, the secondnozzle 21 a 2 ejects a second droplet at a second instance, the thirdnozzle 21 a 3 ejects a third droplet at a third instance, the Nth nozzle21 an eject an Nth droplet at an Nth instance. The time intervalsbetween all adjacent time instances are equal to a same value, such as alag period.

Thus, the multiple droplets can successively reach the annular radiationposition 202 one by one in a sequence. For example, the first dropletejected from the first nozzle 21 a 1 firstly reaches the annularradiation position 202. After a lag period, the second droplet ejectedfrom the second nozzle 21 a 2 reaches the annular radiation position202. After another lag period, the droplet ejected from the third nozzle21 a 3 reaches the annular radiation position 202 After a lag periodwhen the (N−1))th droplet reaches the annular radiation position 202,the Nth droplet ejected from the Nth nozzle 21 an reaches the annularradiation position 202.

In conjunction with reference to FIG. 2 and FIG. 8, when the multiplenozzles 21 are sequentially ejecting droplet 22 downwardly to theannular radiation position 202, the integral rotary structure 215 isrotating. A laser beam generated by the laser source 203 going throughthe focusing lens 236 is also rotating. The rotating laser beam cansequentially bombard the multiple droplets 22 one by one that reachesthe annular radiation position 202.

A specific bombardment process can be the following. The laser beamgenerated by the laser source 203 bombards the first droplet thatreaches the annular radiation position 202. The laser beam rotates alongthe annular radiation position 202 with the rotating focusing lens 236.When the second droplet reaches the annular radiation position 202, thelaser beam bombards the second droplet that reaches the annularradiation position 202. The laser beam continuously rotates along theannular radiation position 202 with the rotating focusing lens 236. Whenthe third droplet reaches the annular radiation position 202, the laserbeam bombards the third droplet that reaches the annular radiationposition 202 . . . . The laser beam continuously rotates along theannular radiation position 202 with the rotating focusing lens 236. Whenthe Nth droplet reaches the annular radiation position 202, the laserbeam bombards the Nth droplet that reaches the annular radiationposition 202.

When the rotating laser beam sequentially bombards the multiple droplets22 one by one that reaches the annular radiation position 202, themultiple bombarded droplets 22 can sequentially generate plasma. Thegenerated plasma can radiate extreme ultraviolet (EUV) light. In thesame time, the condenser mirror 214 is also rotating. The ellipticalreflective surface 231 (refer to FIG. 3) of the condenser mirror 214 cansequentially collect and reflect the extreme ultraviolet light radiatedfrom the multiple bombarded droplets and converge the extremeultraviolet light on the central focus 220.

A specific collecting and reflecting process can be the following. Theelliptical reflective surface 231 collects and reflects the extremeultraviolet light radiated from the bombarded first droplet andconverges the extreme ultraviolet light on the central focus 220. Theelliptical reflective surface 231 rotates with the integral rotarystructure 215. Then the elliptical reflective surface 231 collects andreflects the extreme ultraviolet light radiated from the bombardedsecond droplet and converges the extreme ultraviolet light on thecentral focus 220. The elliptical reflective surface 231 continuouslyrotates with the integral rotary structure 215. The ellipticalreflective surface 231 collects and reflects the extreme ultravioletlight radiated from the bombarded third droplet and converges theextreme ultraviolet light on the central focus 220. The ellipticalreflective surface 231 continuously rotates with the integral rotarystructure 215. The elliptical reflective surface 231 collects andreflects the extreme ultraviolet light radiated from the bombarded Nthdroplet and converges the extreme ultraviolet light on the central focus220.

Referring back to FIG. 8 and FIG. 9, the multiple nozzles 21 in thedroplet nozzle array 201 can repeatedly eject multiple droplets 22downwardly to the annular radiation position 202 by the followingprocess. In a first circulation, the first nozzle 21 a 1 ejects a firstdroplet at a first instance, the second nozzle 21 a 2 ejects a seconddroplet at a second instance, the third nozzle 21 a 3 ejects a thirddroplet at a third instance, . . . , the Nth (N≧3) nozzle 21 an eject anNth droplet at an Nth instance. The time intervals between all adjacenttime instances are equal to a same value, such as a first lag period.And then in a second circulation, the multiple nozzles 21 can repeat theabove process. In some embodiments, the number of circulations can be apredetermined number M (M≧4).

Therefore, considering only one nozzle, the nozzle 21 can eject onedroplet every one fixed time interval, such as a second lag period. Inone embodiments, a value of the second lag period is equal to a value ofthe first lag period times a total number of the multiple nozzles 21.For example, the first nozzle 21 ejects one first droplet, after asecond lag period the first nozzle 21 ejects another first droplet,after another second lag period the first nozzle 21 ejects a third firstdroplet, . . . , after another second lag period the first nozzle 21ejects an Mth (M≧4) first droplet.

The disclosed droplet nozzle array 201 can regularly and constantlyeject droplets downwardly to the annular radiation position 202. Adroplets supply amount per unit time can be increased by using theejecting process described above. Additionally, the laser beam generatedfrom the laser source 203 can also regularly spin, and sequentiallybombard the droplets at the annular radiation position 202. Furthermore,the elliptical reflective surface 231 of the condenser mirror 214 canregularly rotate, collect and reflect the radiated extreme ultravioletlight, and converge the extreme ultraviolet light at the central focus220. Consequently, a power of the extreme ultraviolet light at thecentral focus 220 is improved.

Referring back to FIG. 2, in some embodiments, the laser source 203includes a laser device 204 and a fixed mirror 209 deposited at a 45degree angle. The laser device 204 is located above one side of theintegral rotary structure 215. The fixed mirror 209 can reflect thelaser beam 31 emitted from the laser device 204 into the laser beamincident channel consisting of the second through hole and the thirdthrough hole. The laser beam 31 can go through the laser beam incidentchannel and reach the surface of the focusing lens 236. The fixed mirror209 is disposed on the extension line of the first optical axis 205.

In some other embodiments, the mirror may not be provided. The laserdevice 204 can be directly provided on the extension line of the firstoptical axis 205. The laser beam generated by the laser device 204 candirectly go along a direction coincident with the first optical axis 205through the second through hole and third through hole, and reach thesurface of the focusing lens 236.

In some embodiments, the relative positions of the focusing lens 236 andthe condenser mirror 214 are fixed. The central axis of the focusinglens 236 is offset a first distance from the first optical axis 205.Derived by the brushless motor, the integral rotary structure 215 andthe focusing lens 236 can make synchronous rotation. Thus the laser beamfocused by the focusing lens 236 can spin along the annular radiationposition 202, and bombard the droplets one by one that reaches theannular radiation position 202.

When the focusing lens 236 and condenser mirror 214 are fixedlyconnected, the optical axis of the focusing lens 236 is parallel to thefirst optical axis 205.

The laser device 204 can be a pulses pump laser device having a highpulse frequency. Thus the laser beam generated by the laser device 204can bombard a large number of droplets per unit time. The pulses pumplaser may be a Q-switched laser device or a mode-locked laser device.

The laser pulses emitted from the laser device 204 is synchronized withthe droplet ejection of the droplet nozzle array 201 and the rotation ofthe condenser mirror 214. Thus when a droplet 22 reaches the annularradiation position 202, a corresponding pulse of the laser beam 31 canbombard the droplet 22, and meanwhile the condenser mirror 214 cancollect and reflect the extreme ultraviolet light radiated from thebombarded droplet 22 and converge the extreme ultraviolet light at thecentral focus 220.

In a particular embodiment, the laser device 204 is a CO₂ laser device.An output power of the laser device 204 can between 10 KW and 1000 KW.

In some embodiments, since the multiple nozzles 21 of the droplet nozzlearray 201 can sequentially and continuously eject droplets 22 to theannular radiation position 202, and since the brushless motor can drivethe focusing lens 236 and the condenser mirror 214 to rotate, the laserbeam 31 focused by the focusing lens 236 can spin a circle andsequentially bombard the droplets one by one that reaches the annularradiation position 202. For example, the laser beam 31 can sequentiallybombard the first droplet ejected from the first nozzle 21 a 1, thesecond droplet ejected from the second nozzle 21 a 2, the third dropletejected from the third nozzle 21 a 3, . . . , and the Nth dropletejected from the Nth nozzle 21 an. Then the brushless motor can drivethe focusing lens 236 and the condenser mirror 214 to continuouslyrotate. Thus the laser beam 31 focused by the focusing lens 236 can spinanother circle and sequentially bombard the droplets one by one thatreaches the annular radiation position 202.

In some embodiments, a rotating direction of the focusing lens 236 canbe a clockwise direction. In some other embodiments, a rotatingdirection of the focusing lens 236 can be a counterclockwise direction.

In some embodiments, the EUV light source further comprises a controlunit (not shown in the figures). The control unit is configured forsynchronously outputting a first control signal sequence and a secondcontrol signal sequence. The first control signal sequence is forcontrolling the multiple nozzles 21 to eject droplets 22 sequentially.The second control signal sequence is for controlling the brushlessmotor to drive the focusing lens 236 and the condenser mirror 214rotating synchronously.

In some embodiments, the first control signal sequence and the secondcontrol signal sequence are synchronized with a pulse signal sequencethat drives the laser dives 204 to generate the pulsed laser beam 31.

In some embodiments, the EUV light source further includes a cleaningsystem configured to clean the contaminants on the elliptical reflectivesurface 231 of the condenser mirror 214. For example, some splashingdust generated from the bombarded droplets can be cleaned by thecleaning system.

Referring to FIG. 10, a control signal diagram of an exemplary EUV lightsource is shown in accordance with some embodiments of the disclosedsubject matter. As illustrated, the control signal generated from thecontrol unit can include the first control 31 and the second controlsignal 305. The first control signal can include signal sequence 31 a 1,signal sequence 31 a 2, signal sequence 31 a 3, and signal sequence 31an.

The first signal and the second signal 305 are generated based on a sameclock signal. The number of the first signal is equal to the number ofthe nozzles 21. The signal sequence 31 a 1, signal sequence 31 a 2,signal sequence 31 a 3, . . . , and signal sequence 31 an respectivelycontrol a switch corresponding to the first nozzle 21 a 1, the secondnozzle 21 a 2, the third nozzle 21 a 3, . . . , and the Nth nozzle 21 anrespectively, which are in connection with FIG. 9 described above. Thesecond signal 305 controls the brushless motor to drive the condenserlens 214 and the focusing lens 236 to rotate, which is in connectionwith FIG. 2 described above.

As illustrated in FIG. 10, the signal sequence 31 a 1, signal sequence31 a 2, signal sequence 31 a 3, . . . , and signal sequence 31 ancomprise pulses signals. A time interval between two adjacent pulses isa second lag period T2. A time lag between the signal sequence 31 a 2and the signal sequence 31 a 1 is a first lag period T1. A time lagbetween the signal sequence 31 a 3 and the signal sequence 31 a 2 is afirst lag period T1. Similarly, a time lag between the signal sequence31 an and the prior signal sequence 31 a(n—1) is a first lag period T1.A time interval between two adjacent pulses of each signal sequence is asecond lag period T2.

In some embodiments, a quantitative relationship between the first lagperiod T1 and the second lag period time is NT1=T2. N is a total numberof the first signal, N is also a total number of the multiple nozzles21. Thus the multiple nozzles 21 of the droplet nozzle array 201 cansequentially and cyclically eject droplets 22 to the annular radiationposition 202, the laser beam 31 focused by the focusing lens 236 cancyclically spin and sequentially bombard the droplets one by one thatreaches the annular radiation position 202, and the ellipticalreflective surface 231 of the condenser mirror 214 can cyclicallyrotate, collect and reflect the radiated extreme ultraviolet light, andconverge the extreme ultraviolet light at the central focus 220.

The first signal including signal sequence 31 a 1, signal sequence 31 a2, signal sequence 31 a 3, . . . , and signal sequence 31 an can beapplied to the switches of the multiple nozzles 21 of the droplet nozzlearray 201. Under the control of the first signal, the droplet nozzlearray 201 can eject droplets 22 downwardly to the annular radiationposition 202 by the following process. In a first circulation, the firstnozzle 21 a 1 ejects a first droplet at a first instance, the secondnozzle 21 a 2 ejects a second droplet at a second instance, the thirdnozzle 21 a 3 ejects a third droplet at a third instance, . . . , theNth (N≧3) nozzle 21 an eject an Nth droplet at an Nth instance. The timeintervals between all adjacent time instances are the first lag periodT1. And then in a second circulation, the multiple nozzles 21 can repeatthe above process. The time interval between two adjacent circulationsis the second lag period T2.

When the first signal is applied to the droplet nozzle array 201, thesecond signal 305 is also applied to the brushless motor.

Before the droplet nozzle array 201 ejecting droplets, the condensermirror 214 and the focusing lens 236 are in a first initial position.When the EUV light source starts to work, the condenser mirror 214 andthe focusing lens 236 accelerate and move from the first initialposition to a second initial position, and then the condenser mirror 214and the focusing lens 236 make a uniform rotational motion from thesecond initial position. When the focusing lens 236 is located in thesecond initial position, the laser beam 31 focused by the focusing lens236 can bombard the first droplet ejected from the first nozzle 21 a atthe annular radiation position 202. In the same time, the condensermirror 214 can collect and reflect the generated extreme ultravioletlight radiated from the bombarded first droplet, and converge theextreme ultraviolet light at the central focus 220.

In some embodiments, a rising edge of the second signal 305 lags behindthe first pulse of the signal sequence 31 a 1. A lag period from thesecond signal 305 to the first pulse of the signal sequence 31 a 1 is atime range for the first droplet moving from the first nozzle 21 a tothe annular radiation position 202.

In some embodiments, a working process of the EUV light source caninclude the following steps. The droplet nozzle array 201 receives thefirst signal, and the brushless motor receives the second signalsequence 305. The first signal can control the multiple nozzles 21sequentially and continuously eject droplets 22 to the annular radiationposition 202. When the first droplet reaches the annular radiationposition 202, the focusing lens 236 and the condenser mirror 214 rotateto the second initial position. The laser beam 31 focused by thefocusing lens 236 can bombard the first droplet at the annular radiationposition 202. In the meanwhile the condenser mirror 214 can collect andreflect the EUV light radiated from the bombarded first droplet, andconverge the EUV light at the central focus 220. Next, the second signal305 can control the brushless motor to drive the focusing lens 236 andthe condenser mirror 214 rotating at a constant speed. Thus the laserbeam 31 focused by the focusing lens 236 also spins and sequentiallybombards the droplets one by one that reaches the annular radiationposition 202. And the condenser mirror 214 can collect and reflect theEUV light radiated from the bombarded droplets one by one, and convergethe EUV light at the central focus 220.

The condenser mirror 214 can rotate at a constant speed. An angularvelocity of the condenser mirror 214 is equal to a rotational angle ofthe condenser mirror 214 to collect the EUV light radiated from twoadjacent bombarded droplets divided by the first lag period T1.

In some embodiments of the disclosed subject matter, an exposureapparatus is provided. The exposure apparatus includes an EUV lightsource described above. The disclosed EUV light source can be used as anexposure light source of the exposure apparatus. A specific structure ofthe exposure apparatus can be referred to some existing structures ofthe exposure apparatus.

Referring to FIGS. 11-17, schematic structures of an exemplaryintegrated rotary structure corresponding to certain stages of afabricating process are shown in consistent with some embodiments of thedisclosed subject matter.

Referring to FIG. 11, a cylinder material 300 can be provided. Thecylinder material 300 comprises a circular side wall 34, and two flatsurfaces including a third surface 37 and a forth surface 32. An axis206 of the cylinder material 300 goes through the centers of the thirdsurface 37 and the forth surface 32.

The cylinder material 300 has a cylindrical shape. A material of thecylinder material 300 can be metal, quartz, or any other suitablematerial.

Referring to FIG. 12, the third surface 37 of the cylinder material 300can be machined. An elliptical reflective surface 231 can be formed inthe cylinder material 300. The second optical axis of the ellipticalreflective surface 231 coincides with the axis 206 of the cylindermaterial 300.

The ellipsoidal reflective surface 231 sinks into the cylinder material300 and has a first depth, which means that an edge of the ellipticalreflective surface 231 has a second distance far from the third surface37. The second distance ensures an enough space for subsequent formingprocess of the non-reflective surface, and can avoid a potential damageto the elliptical reflective surface 231 during the subsequent formingprocess of the non-reflective surface.

A first through hole 237 can be formed in the cylinder material 300. Thefirst through hole 238 goes through the center of the ellipticalreflective surface 231. A size of the first through hole 237 is smallerthan the size of the elliptical reflective surface 231. An axis of thefirst through hole 237 coincides with the second optical axis 206.

Referring to FIG. 13 and FIG. 14, the circular side wall 34 of thecylinder material 300 can be machined to form a fifth surface 35 and asixth surface 36. There is a first angle between the fifth surface 35and the sixth surface 36. A central symmetric axis of the fifth surface35 and the sixth surface 36 is the first optical axis 205.

Referring to FIG. 13, the two regions in the thick solid line 35 are tobe formed as the fifth surface 35 and the sixth surface 36. The fifthsurface 35 and the sixth surface 36 are used for holding planes in thesubsequent processes. The fifth surface 35 and the sixth surface 36 areparallel to each other. Both the fifth surface 35 and the sixth surface36 have a first angle with the extension line of the second optical axis206. In another word, the center of the elliptical reflective surface231 is offset with respect to the first optical axis 205. Additionally,a distance between the second optical axis 206 and an overlap line ofthe fifth surface 35 and the third surface 37 is greater than a distancebetween the second optical axis 206 and an overlap line of the sixthsurface 36 and the third surface 37.

Referring to FIG. 15 and FIG. 16, using the fifth surface 35 and thesixth surface 36 as holding planes, the third surface 37 of the cylindermaterial 300 can be machined to form a non-reflective surface 232. Thenon-reflective surface 232 has a curved shape, and is in contact withthe edge of the elliptical reflective surface 231. The ellipticalreflective surface 231 and the non-reflective surface 232 constitute thefirst surface 233 of the condenser mirror 214.

When the fifth surface 35 and the sixth surface 36 are used as holdingplanes, the elliptical reflective surface 231 is eccentric and inclinedrelating to the first optical axis 205. An inclined angle of theelliptical reflective surface 231 is equal to an angle between the firstoptical axis 205 and the second optical axis 206. With respect to thethird surface 37, the edge of the elliptical spherical reflectivesurface 231 has a high point and a low point. The low point is a pointof the edge of the elliptical reflective surface 231 that is nearest tothe third surface 37, and the high point is a point of the edge of theelliptical reflective surface 231 that is farthest to the third surface37.

In some embodiments, there are two steps for forming the non-reflectivesurface 231. The first step is forming a first cambered surface 33 thatis in contact with or close to the high point of the ellipticalspherical reflective surface 231. The second step is forming a secondcambered surface that is in contact with or close to the low point ofthe elliptical spherical reflective surface 231. The second camberedsurface can be machined in the shaded region as illustrated in FIG. 15.

In some embodiments, after forming the non-reflective surface 232, aroughening treatment can be performed on the non-reflective surface 232.An increasing of the roughness of the non-reflecting surface 232 canreduce a reflection rate of the EUV radiation. The roughening treatmentcan be a grinding process or a spraying process. Prior to performing theroughening treatment, a protective film can be formed on the ellipticalreflective surface 231.

In some embodiments, after forming the non-reflective surface 232, aportion of the cylinder material 300 can be removed along the fifthsurface 35 and the sixth surface 36. Thus a second surface 234 can beformed opposite to the first surface 233. The second surface 234 canhave a curved shape.

Next, the remaining portion of the cylinder material 300 can be machinedalong the fifth surface 35 and the sixth surface 36 to form a motordriving shaft 217 connecting with the second surface 324.

Referring to FIG. 17, the remaining portion of the cylinder material 300can be machined along the fourth surface 34, the fifth surface 35, andthe sixth surface 36 to form a thrust bearing 230 connecting with themotor driving shaft 217.

In some embodiments, the thrust bearing 230 are two inner ringsconnected with the motor driving shaft 217. The two inner rings includea first inner ring 235, and a second inner 238 integrally connected withthe first inner ring 235. The second inner ring 238 is located above thefirst inner ring 235.

A portion of the first inner ring 235 and a portion of the second innerring 238 are protruded from the outer surface of the motor driving shaft217. The outer surfaces of the first inner ring 235 and the second innerring 238 are inclined to the first axis 205. An angle between the outersurface of the first inner ring 235 and the outer surface of the secondinner ring 238 is less than 90 degrees. In one embodiment, across-sectional view of the outer surface of the first inner ring 235and the outer surface of the second inner ring 238 is “<>” shape.

In some embodiments, the inner rings of the thrust bearing 230 and themotor driving shaft 217 can be further machined. A second through holecan be formed in the motor driving shaft 217. A third through hole canbe formed in the thrust bearing 230. The third through hole is connectedwith the second through, and the second through hole is connected withthe first through hole.

It should be noted that, the disclosed method for fabricating theintegrated rotary structure 215 can be performed by any suitableequipment including computer numerical control (CNC) machine tools.

The provision of the examples described herein (as well as clausesphrased as “such as,” “e.g.,” “including,” and the like) should not beinterpreted as limiting the claimed subject matter to the specificexamples; rather, the examples are intended to illustrate only some ofmany possible aspects.

Accordingly, an extreme ultraviolet lithography (EUV) light source, anexposure apparatus, and a method for fabricating an integrated rotarystructure are provided.

Although the disclosed subject matter has been described and illustratedin the foregoing illustrative embodiments, it is understood that onedisclosure has been made only by way of example, and that numerouschanges in the details of embodiment of the disclosed subject matter canbe made without departing from the spirit and scope of the disclosedsubject matter, which is only limited by the claims which follow.Features of the disclosed embodiments can be combined and rearranged invarious ways. Without departing from the spirit and scope of thedisclosed subject matter, modifications, equivalents, or improvements tothe disclosed subject matter are understandable to those skilled in theart and are intended to be encompassed within the scope of onedisclosure.

What is claimed is:
 1. An extreme ultraviolet light source, comprising:a droplet nozzle array droplet nozzle array comprising a plurality ofnozzles arranged in a ring, wherein the plurality of nozzles areconfigured for sequentially ejecting droplets towards an annularradiation position; a laser source for generating a laser beam, whereinthe laser beam is controlled to rotate and sequentially bombard thedroplets that reach the annular radiation position, wherein thebombarded droplets form a plasma that radiates an extreme ultravioletlight; and an integrated rotary structure located between the dropletnozzle array and the laser source, wherein the integrated rotarystructure includes: a condenser mirror comprising a first surface and asecond surface opposing to the first surface, and ‘a motor driving shaftthat is integrally connected with the condenser mirror, wherein thefirst surface faces the droplet nozzle array, the second surface isconnected with the motor driving shaft, the first surface comprises aneccentric and inclined elliptical reflective surface and anon-reflective surface surrounding the elliptical reflective surface,and the elliptical reflective surface is configured for collecting andreflecting the extreme ultraviolet light, and converging the extremeultraviolet light at a central focus under the annular radiationposition.
 2. The extreme ultraviolet light source of claim 1, whereinthe integrated rotary structure further comprises a thrust bearingintegrally connected with the motor driving shaft.
 3. The extremeultraviolet light source of claim 2, wherein: the plurality of nozzlesare equidistantly arranged in the ring; and each nozzle is inclined at afirst angle toward a center of the ring.
 4. The extreme ultravioletlight source of claim 3, wherein: the annular radiation position has aring shape; the annular radiation position is parallel to the ring ofthe plurality of nozzles; and a radius of the annular radiation positionis smaller than a radius of the ring of the plurality of nozzles.
 5. Theextreme ultraviolet light source of claim 4, wherein a connectionbetween a center of the annular radiation position and a center of thering of the plurality of nozzles is perpendicular with the annularradiation position.
 6. The extreme ultraviolet light source of claim 5,wherein the central focus is located on an extension line of theconnection between a center of the annular radiation position and acenter of the ring of the plurality of nozzles.
 7. The extremeultraviolet light source of claim 6, wherein the connection between thecenter of the annular radiation position and the center of the ring ofthe plurality of nozzles coincides with a first optical axis of theelliptical reflective surface.
 8. The extreme ultraviolet light sourceof claim 7, further comprising a brushless motor configured for drivingthe integrated rotary structure to rotate with respect of the firstoptical axis.
 9. The extreme ultraviolet light source of claim 8,wherein: the elliptical reflective surface has a second optical axisgoing through the central focus; and an inclined angle of the ellipticalreflective surface is equal to an angle between the first optical axisand the second optical axis.
 10. The extreme ultraviolet light source ofclaim 9, further comprising: a first through hole in the center of theelliptical reflective surface; a second through hole in the motordriving shaft; and a third through hole in the thrust bearing; whereinthe first through hole, the second through hole, and the third throughhole are interconnected with each other to form a laser beam incidentchannel; and wherein the laser source comprises: a laser deviceconfigured for generating the laser beam; a focusing lens located in thefirst through hole and fixed with the condenser mirror, wherein thefocusing lens is configured for focusing the laser beam to the annularradiation position.
 11. The extreme ultraviolet light source of claim10, wherein the laser source further comprises a reflecting device forreflecting the laser beam generated by the laser device into the laserbeam incident channel.
 12. The extreme ultraviolet light source of claim10, further comprising: a control unit configured for synchronouslyoutputting a first signal and a second signal, wherein: the first signalcontrols the plurality of nozzles to sequentially eject droplets, andthe second signal controls the brushless motor to drive the integratedrotary structure to make the elliptical reflective surface and thefocusing lens rotate synchronously.
 13. The extreme ultraviolet lightsource of claim 10, wherein the laser device is a pulses pump laserdevice.
 14. The extreme ultraviolet light source of claim 1, wherein thefirst signal controls the plurality of nozzles to sequentially ejectdroplets in a certain direction, wherein each nozzle ejects a dropletafter a first lag period of an instance that an adjacent nozzle ejects adroplet.
 15. The extreme ultraviolet light source of claim 14, whereinthe first lag period equals a time interval between two adjacent laserpulses generated from the pulses pump laser device.
 16. The extremeultraviolet light source of claim 15, wherein: the first signal controlseach nozzle to continuously eject droplets; a time interval between twoadjacent ejecting is a second lag period; and the second lag periodequals to a number of the plurality of nozzles times the first lagperiod.
 17. An exposure apparatus, comprising: an extreme ultravioletlight source, comprising: a droplet nozzle array comprising a pluralityof nozzles arranged in a ring, wherein the plurality of nozzles areconfigured for sequentially ejecting droplets towards an annularradiation position; a laser source for generating a laser beam, whereinthe laser beam is controlled to rotate and sequentially bombard thedroplets that reach the annular radiation position, wherein thebombarded droplets form a plasma that radiates an extreme ultravioletlight; and an integrated rotary structure located between the dropletnozzle array and the laser source, wherein the integrated rotarystructure comprises: a condenser mirror comprising a first surface and asecond surface opposing to the first surface, and a motor driving shaftthat is integrally connected with the condenser mirror, wherein thefirst surface faces the droplet nozzle array, the second surface isconnected with the motor driving shaft, the first surface comprises aneccentric and inclined elliptical reflective surface and anon-reflective surface surrounding the elliptical reflective surface,and the elliptical reflective surface is configured for collecting andreflecting the extreme ultraviolet light radiated, and converging theextreme ultraviolet light at a central focus under the annular radiationposition.
 18. A method for fabricating an integrated rotary structure,comprising: providing a cylinder material, comprising a circular sidewall, a third surface at one end of the circular side wall and a fourthsurface at another end of the circular side wall opposing to the thirdsurface; machining the third surface of the cylinder material to form anelliptical reflective surface, wherein: a second optical axis of theelliptical reflective surface coincides with an axis of the cylindermaterial passing through centers of the third and fourth surfaces, andthe ellipsoidal reflective surface sinks into the cylinder material andby a first depth; forming a first through hole going through a center ofthe elliptical reflective surface; machining the circular side wall ofthe cylinder material to form a fifth surface and a sixth surface,wherein: both the fifth surface and the sixth surface have a first anglewith the second optical axis, and a central symmetrical axis of thefifth surface and the sixth surface coincides with a first optical axisof the elliptical reflective surface; and using the fifth surface andthe sixth surface as holding planes, machining the third surface to forma curved non-reflective surface surrounding the elliptical reflectivesurface.
 19. The method of claim 18, wherein forming the curvednon-reflective surface comprises: forming a first cambered surface thatis in contact with or close to a high point of the elliptical sphericalreflective surface; and forming a second cambered surface that is incontact with or close to a low point of the elliptical sphericalreflective surface.
 20. The method of claim 18, further comprising:removing a portion of the cylinder material along the fifth surface andthe sixth surface to form a curved second surface, wherein the secondsurface opposites a first surface comprising the non-reflective surfaceand the elliptical reflective surface; machining a remaining portion ofthe cylinder material along the fifth surface and the sixth surface toform a motor driving shaft connecting with the second surface; andmachining a remaining portion of the cylinder material along the fourthsurface, the fifth surface, and the sixth surface to form a thrustbearing connecting with the motor driving shaft.